This invention relates to battery powered vehicles and, more particularly, to an apparatus which can be used to remove a spent battery from a vehicle in an underground coal mine and replace it with a charged battery.
Underground coal mine vehicles are normally operated by electrical power which can be supplied by batteries as an alternative to providing power through an unwieldy power line. The capacity of such batteries is normally designed to be great enough so that a machine may be operated for an entire shift before the battery needs to be charged. After each shift, spent batteries are normally removed from the machine and replaced by charged batteries and the spent batteries are charged for use on the next shift. Mine car batteries require special handling considerations since a single car can utilize two batteries weighing over 3,000 lbs. a piece which are contained in a steel casing.
Various ways of mechanically replacing spent batteries have been developed such as the hydraulic transfer mechanism in U.S. Pat. No. 3,799,063 and the hydraulic jacks in U.S. Pat. No. 3,336,997 which remove a battery and position it on a sled for holding the batteries for charging.
Both of these procedures, however, require power cables to be attached to the vehicle so that it can be driven to another location in the mine where a charged battery can be loaded. This is necessary because of the nature of underground mining operations in the United States which use the room and pillar method where mine car entries are normally only narrow enough to accommodate a set of batteries from one vehicle.
Once a battery is removed to the mine floor or sled, it is usually charged at that location so the heavy battery does not have to be moved about in the mine. Since the distance between adjacent entries can be 40-45 feet, relatively long lengths of cables for moving the mine vehicles are required and a separate battery charging station must be maintained in each entry which necessitates fire-proofing each entry as well as providing adequate ventilation. It has also been found that when sleds are used they are often bumped out of position and must be dragged back into position.